diff --git a/kernel/src/arch/x86_64/gdt.rs b/kernel/src/arch/x86_64/gdt.rs
index 9db86dc..aa46848 100644
--- a/kernel/src/arch/x86_64/gdt.rs
+++ b/kernel/src/arch/x86_64/gdt.rs
@@ -1,5 +1,4 @@
 use super::ipi::IPIEventItem;
-use alloc::boxed::Box;
 use alloc::vec::*;
 use core::sync::atomic::{AtomicBool, Ordering};
 use x86_64::registers::model_specific::Msr;
@@ -8,7 +7,7 @@ use x86_64::structures::tss::TaskStateSegment;
 use x86_64::{PrivilegeLevel, VirtAddr};
 
 use crate::consts::MAX_CPU_NUM;
-use crate::sync::{Semaphore, SpinLock as Mutex};
+use crate::sync::SpinLock as Mutex;
 
 /// Init TSS & GDT.
 pub fn init() {
@@ -79,7 +78,7 @@ impl Cpu {
         self.preemption_disabled.load(Ordering::Relaxed)
     }
     unsafe fn init(&'static mut self) {
-        use x86_64::instructions::segmentation::{load_fs, set_cs};
+        use x86_64::instructions::segmentation::set_cs;
         use x86_64::instructions::tables::load_tss;
 
         // Set the stack when DoubleFault occurs
diff --git a/kernel/src/arch/x86_64/interrupt/fast_syscall.rs b/kernel/src/arch/x86_64/interrupt/fast_syscall.rs
index d096b65..f4a8249 100644
--- a/kernel/src/arch/x86_64/interrupt/fast_syscall.rs
+++ b/kernel/src/arch/x86_64/interrupt/fast_syscall.rs
@@ -1,5 +1,4 @@
 use super::super::gdt;
-use super::TrapFrame;
 use core::mem::transmute;
 /// `syscall` instruction
 use x86_64::registers::model_specific::*;
diff --git a/kernel/src/arch/x86_64/io.rs b/kernel/src/arch/x86_64/io.rs
index c78b014..855854f 100644
--- a/kernel/src/arch/x86_64/io.rs
+++ b/kernel/src/arch/x86_64/io.rs
@@ -1,5 +1,4 @@
 use super::driver::serial::*;
-use super::driver::vga::VGA_WRITER;
 use core::fmt::{Arguments, Write};
 
 pub fn getchar() -> char {
@@ -19,6 +18,7 @@ pub fn putfmt(fmt: Arguments) {
     }
     #[cfg(not(feature = "nographic"))]
     {
+        use super::driver::vga::VGA_WRITER;
         unsafe {
             VGA_WRITER.force_unlock();
         }
diff --git a/kernel/src/arch/x86_64/ipi.rs b/kernel/src/arch/x86_64/ipi.rs
index 816d887..3970272 100644
--- a/kernel/src/arch/x86_64/ipi.rs
+++ b/kernel/src/arch/x86_64/ipi.rs
@@ -9,7 +9,7 @@ use core::sync::atomic::{spin_loop_hint, AtomicU8, Ordering};
 pub type IPIEventItem = Box<FnBox()>;
 
 unsafe fn get_apic() -> XApic {
-    let mut lapic = unsafe { XApic::new(phys_to_virt(LAPIC_ADDR)) };
+    let mut lapic = XApic::new(phys_to_virt(LAPIC_ADDR));
     lapic
 }
 
diff --git a/kernel/src/arch/x86_64/mod.rs b/kernel/src/arch/x86_64/mod.rs
index b92e5fd..b6b77fb 100644
--- a/kernel/src/arch/x86_64/mod.rs
+++ b/kernel/src/arch/x86_64/mod.rs
@@ -16,7 +16,7 @@ pub mod rand;
 pub mod syscall;
 pub mod timer;
 
-static AP_CAN_INIT: AtomicBool = ATOMIC_BOOL_INIT;
+static AP_CAN_INIT: AtomicBool = AtomicBool::new(false);
 
 /// The entry point of kernel
 #[no_mangle] // don't mangle the name of this function
diff --git a/kernel/src/arch/x86_64/paging.rs b/kernel/src/arch/x86_64/paging.rs
index 3e34535..2f8c26e 100644
--- a/kernel/src/arch/x86_64/paging.rs
+++ b/kernel/src/arch/x86_64/paging.rs
@@ -21,7 +21,7 @@ pub trait PageExt {
 impl PageExt for Page {
     fn of_addr(address: usize) -> Self {
         use x86_64;
-        Page::containing_address(x86_64::VirtAddr::new(address as u64))
+        Page::containing_address(VirtAddr::new(address as u64))
     }
     fn range_of(begin: usize, end: usize) -> PageRange {
         Page::range(Page::of_addr(begin), Page::of_addr(end - 1) + 1)
@@ -101,7 +101,7 @@ fn frame_to_page_table(frame: Frame) -> *mut x86PageTable {
 
 impl Entry for PageEntry {
     fn update(&mut self) {
-        use x86_64::{instructions::tlb::flush, VirtAddr};
+        use x86_64::instructions::tlb::flush;
         let addr = self.1.start_address();
         flush(addr);
         flush_tlb_all(addr.as_u64() as usize);
@@ -199,7 +199,7 @@ impl PageTableImpl {
     /// WARN: You MUST call `core::mem::forget` for it after use!
     pub unsafe fn active() -> Self {
         let frame = Cr3::read().0;
-        let table = unsafe { &mut *frame_to_page_table(frame) };
+        let table = &mut *frame_to_page_table(frame);
         PageTableImpl(
             MappedPageTable::new(table, frame_to_page_table),
             core::mem::MaybeUninit::uninitialized().into_initialized(),
diff --git a/kernel/src/drivers/input/virtio_input.rs b/kernel/src/drivers/input/virtio_input.rs
index cf6053d..9c3fd5d 100644
--- a/kernel/src/drivers/input/virtio_input.rs
+++ b/kernel/src/drivers/input/virtio_input.rs
@@ -11,7 +11,6 @@ use bitflags::*;
 use device_tree::util::SliceRead;
 use device_tree::Node;
 use log::*;
-use rcore_memory::paging::PageTable;
 use rcore_memory::PAGE_SIZE;
 use volatile::Volatile;
 
diff --git a/kernel/src/drivers/net/router.rs b/kernel/src/drivers/net/router.rs
index 23a7625..6577d5b 100644
--- a/kernel/src/drivers/net/router.rs
+++ b/kernel/src/drivers/net/router.rs
@@ -5,12 +5,12 @@ use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
 
+use bitflags::*;
 use smoltcp::iface::*;
 use smoltcp::phy::{self, DeviceCapabilities};
 use smoltcp::time::Instant;
 use smoltcp::wire::*;
 use smoltcp::Result;
-use bitflags::*;
 
 use crate::net::SOCKETS;
 use crate::sync::SpinNoIrqLock as Mutex;
@@ -119,7 +119,12 @@ impl phy::TxToken for RouterTxToken {
     {
         let mut buffer = vec![0; len];
         let res = f(&mut buffer);
-        debug!("out buf {} data {:x?} port {}", len, &buffer[..20], (self.0).1);
+        debug!(
+            "out buf {} data {:x?} port {}",
+            len,
+            &buffer[..20],
+            (self.0).1
+        );
 
         unsafe {
             AXI_STREAM_FIFO_TDR.write_volatile(2);
@@ -145,7 +150,10 @@ impl Driver for RouterInterface {
         let isr = unsafe { AXI_STREAM_FIFO_ISR.read_volatile() };
 
         if isr > 0 {
-            debug!("handle router interrupt {:?}", AXIStreamFifoInterrupt::from_bits_truncate(isr));
+            debug!(
+                "handle router interrupt {:?}",
+                AXIStreamFifoInterrupt::from_bits_truncate(isr)
+            );
             unsafe {
                 AXI_STREAM_FIFO_ISR.write(isr);
                 let rdfo = AXI_STREAM_FIFO_RDFO.read_volatile();
@@ -157,7 +165,12 @@ impl Driver for RouterInterface {
                     for i in 1..rdfo {
                         buffer.push(AXI_STREAM_FIFO_RDFD.read_volatile() as u8);
                     }
-                    debug!("got packet of length {} port {} data {:x?}", rdfo, port, &buffer[..20]);
+                    debug!(
+                        "got packet of length {} port {} data {:x?}",
+                        rdfo,
+                        port,
+                        &buffer[..20]
+                    );
                     driver.buffer[port as usize].push(buffer);
                 }
                 drop(driver);
@@ -214,11 +227,14 @@ pub fn router_init() {
     for i in 0..ENABLED_PORTS {
         let ethernet_addr = EthernetAddress::from_bytes(&[2, 2, 3, 3, 0, i]);
 
-        let net_driver = RouterDriver(Arc::new(Mutex::new(Router { buffer: [Vec::new(), Vec::new()] })), i);
+        let net_driver = RouterDriver(
+            Arc::new(Mutex::new(Router {
+                buffer: [Vec::new(), Vec::new()],
+            })),
+            i,
+        );
 
-        let ip_addrs = [
-            IpCidr::new(IpAddress::v4(10, 0, i, 1), 24),
-        ];
+        let ip_addrs = [IpCidr::new(IpAddress::v4(10, 0, i, 1), 24)];
         let neighbor_cache = NeighborCache::new(BTreeMap::new());
         let routes = Routes::new(BTreeMap::new());
         let iface = EthernetInterfaceBuilder::new(net_driver.clone())
diff --git a/kernel/src/memory.rs b/kernel/src/memory.rs
index b2f1c3c..99c41f0 100644
--- a/kernel/src/memory.rs
+++ b/kernel/src/memory.rs
@@ -14,10 +14,9 @@
 
 use super::HEAP_ALLOCATOR;
 pub use crate::arch::paging::*;
-use crate::consts::{KERNEL_OFFSET, MEMORY_OFFSET, PHYSICAL_MEMORY_OFFSET};
+use crate::consts::{MEMORY_OFFSET, PHYSICAL_MEMORY_OFFSET};
 use crate::process::current_thread;
-use crate::sync::{MutexGuard, SpinNoIrq, SpinNoIrqLock};
-use alloc::boxed::Box;
+use crate::sync::SpinNoIrqLock;
 use bitmap_allocator::BitAlloc;
 use buddy_system_allocator::Heap;
 use core::mem;
@@ -132,13 +131,13 @@ pub fn handle_page_fault(addr: usize) -> bool {
 
 pub fn init_heap() {
     use crate::consts::KERNEL_HEAP_SIZE;
-    const machine_align: usize = mem::size_of::<usize>();
-    const heap_block: usize = KERNEL_HEAP_SIZE / machine_align;
-    static mut HEAP: [usize; heap_block] = [0; heap_block];
+    const MACHINE_ALIGN: usize = mem::size_of::<usize>();
+    const HEAP_BLOCK: usize = KERNEL_HEAP_SIZE / MACHINE_ALIGN;
+    static mut HEAP: [usize; HEAP_BLOCK] = [0; HEAP_BLOCK];
     unsafe {
         HEAP_ALLOCATOR
             .lock()
-            .init(HEAP.as_ptr() as usize, heap_block * machine_align);
+            .init(HEAP.as_ptr() as usize, HEAP_BLOCK * MACHINE_ALIGN);
     }
     info!("heap init end");
 }
diff --git a/kernel/src/process/mod.rs b/kernel/src/process/mod.rs
index 494f7b7..e08f628 100644
--- a/kernel/src/process/mod.rs
+++ b/kernel/src/process/mod.rs
@@ -1,7 +1,6 @@
 pub use self::structs::*;
 use crate::arch::cpu;
 use crate::consts::{MAX_CPU_NUM, MAX_PROCESS_NUM};
-use crate::sync::{MutexGuard, SpinNoIrq};
 use alloc::{boxed::Box, sync::Arc};
 use log::*;
 pub use rcore_thread::*;
diff --git a/kernel/src/shell.rs b/kernel/src/shell.rs
index ddad4cc..f811969 100644
--- a/kernel/src/shell.rs
+++ b/kernel/src/shell.rs
@@ -1,6 +1,5 @@
 //! Kernel shell
 
-use crate::arch::io;
 use crate::fs::ROOT_INODE;
 use crate::process::*;
 use alloc::string::String;
diff --git a/kernel/src/sync/condvar.rs b/kernel/src/sync/condvar.rs
index 0f19b03..b7c6f0f 100644
--- a/kernel/src/sync/condvar.rs
+++ b/kernel/src/sync/condvar.rs
@@ -1,5 +1,4 @@
 use super::*;
-use crate::arch::cpu;
 use crate::process::processor;
 use crate::thread;
 use alloc::collections::VecDeque;
@@ -105,7 +104,7 @@ impl Condvar {
         let mut count = 0;
         let queue = self.wait_queue.lock();
         for t in queue.iter() {
-            if (count >= n) {
+            if count >= n {
                 break;
             }
             t.unpark();
diff --git a/kernel/src/syscall/fs.rs b/kernel/src/syscall/fs.rs
index 04a54b6..375d870 100644
--- a/kernel/src/syscall/fs.rs
+++ b/kernel/src/syscall/fs.rs
@@ -388,7 +388,7 @@ impl Syscall<'_> {
         flags: usize,
     ) -> SysResult {
         let proc = self.process();
-        let path = unsafe { check_and_clone_cstr(path)? };
+        let path = check_and_clone_cstr(path)?;
         let stat_ref = unsafe { self.vm().check_write_ptr(stat_ptr)? };
         let flags = AtFlags::from_bits_truncate(flags);
         info!(
@@ -539,7 +539,7 @@ impl Syscall<'_> {
 
     pub fn sys_chdir(&mut self, path: *const u8) -> SysResult {
         let mut proc = self.process();
-        let path = unsafe { check_and_clone_cstr(path)? };
+        let path = check_and_clone_cstr(path)?;
         if !proc.pid.is_init() {
             // we trust pid 0 process
             info!("chdir: path: {:?}", path);
@@ -592,8 +592,8 @@ impl Syscall<'_> {
         newpath: *const u8,
     ) -> SysResult {
         let proc = self.process();
-        let oldpath = unsafe { check_and_clone_cstr(oldpath)? };
-        let newpath = unsafe { check_and_clone_cstr(newpath)? };
+        let oldpath = check_and_clone_cstr(oldpath)?;
+        let newpath = check_and_clone_cstr(newpath)?;
         info!(
             "renameat: olddirfd: {}, oldpath: {:?}, newdirfd: {}, newpath: {:?}",
             olddirfd as isize, oldpath, newdirfd as isize, newpath
@@ -613,7 +613,7 @@ impl Syscall<'_> {
 
     pub fn sys_mkdirat(&mut self, dirfd: usize, path: *const u8, mode: usize) -> SysResult {
         let proc = self.process();
-        let path = unsafe { check_and_clone_cstr(path)? };
+        let path = check_and_clone_cstr(path)?;
         // TODO: check pathname
         info!(
             "mkdirat: dirfd: {}, path: {:?}, mode: {:#o}",
@@ -631,7 +631,7 @@ impl Syscall<'_> {
 
     pub fn sys_rmdir(&mut self, path: *const u8) -> SysResult {
         let proc = self.process();
-        let path = unsafe { check_and_clone_cstr(path)? };
+        let path = check_and_clone_cstr(path)?;
         info!("rmdir: path: {:?}", path);
 
         let (dir_path, file_name) = split_path(&path);
@@ -657,8 +657,8 @@ impl Syscall<'_> {
         flags: usize,
     ) -> SysResult {
         let proc = self.process();
-        let oldpath = unsafe { check_and_clone_cstr(oldpath)? };
-        let newpath = unsafe { check_and_clone_cstr(newpath)? };
+        let oldpath = check_and_clone_cstr(oldpath)?;
+        let newpath = check_and_clone_cstr(newpath)?;
         let flags = AtFlags::from_bits_truncate(flags);
         info!(
             "linkat: olddirfd: {}, oldpath: {:?}, newdirfd: {}, newpath: {:?}, flags: {:?}",
diff --git a/kernel/src/syscall/mem.rs b/kernel/src/syscall/mem.rs
index 3a3d4a8..1a031da 100644
--- a/kernel/src/syscall/mem.rs
+++ b/kernel/src/syscall/mem.rs
@@ -1,7 +1,5 @@
 use rcore_memory::memory_set::handler::{Delay, File};
 use rcore_memory::memory_set::MemoryAttr;
-use rcore_memory::paging::PageTable;
-use rcore_memory::Page;
 use rcore_memory::PAGE_SIZE;
 
 use crate::memory::GlobalFrameAlloc;
diff --git a/kernel/src/syscall/mod.rs b/kernel/src/syscall/mod.rs
index 5b7def8..b50c80a 100644
--- a/kernel/src/syscall/mod.rs
+++ b/kernel/src/syscall/mod.rs
@@ -16,13 +16,13 @@ use crate::sync::{Condvar, MutexGuard, SpinNoIrq};
 use crate::thread;
 use crate::util;
 
-use self::custom::*;
-use self::fs::*;
-use self::mem::*;
-use self::misc::*;
+pub use self::custom::*;
+pub use self::fs::*;
+pub use self::mem::*;
+pub use self::misc::*;
 pub use self::net::*;
-use self::proc::*;
-use self::time::*;
+pub use self::proc::*;
+pub use self::time::*;
 
 mod custom;
 mod fs;
@@ -32,7 +32,9 @@ mod net;
 mod proc;
 mod time;
 
+#[cfg(feature = "profile")]
 use alloc::collections::BTreeMap;
+#[cfg(feature = "profile")]
 use spin::Mutex;
 
 #[cfg(feature = "profile")]
diff --git a/kernel/src/syscall/net.rs b/kernel/src/syscall/net.rs
index 2edb9d6..3197ab7 100644
--- a/kernel/src/syscall/net.rs
+++ b/kernel/src/syscall/net.rs
@@ -6,7 +6,7 @@ use crate::fs::FileLike;
 use crate::memory::MemorySet;
 use crate::net::{
     Endpoint, LinkLevelEndpoint, NetlinkEndpoint, NetlinkSocketState, PacketSocketState,
-    RawSocketState, Socket, TcpSocketState, UdpSocketState, SOCKETS,
+    RawSocketState, Socket, TcpSocketState, UdpSocketState,
 };
 use alloc::boxed::Box;
 use core::cmp::min;
@@ -462,13 +462,13 @@ impl SockAddr {
             return Ok(0);
         }
 
-        let addr_len = unsafe { vm.check_write_ptr(addr_len)? };
+        let addr_len = vm.check_write_ptr(addr_len)?;
         let max_addr_len = *addr_len as usize;
         let full_len = self.len()?;
 
         let written_len = min(max_addr_len, full_len);
         if written_len > 0 {
-            let target = unsafe { vm.check_write_array(addr as *mut u8, written_len)? };
+            let target = vm.check_write_array(addr as *mut u8, written_len)?;
             let source = slice::from_raw_parts(&self as *const SockAddr as *const u8, written_len);
             target.copy_from_slice(source);
         }
diff --git a/kernel/src/syscall/proc.rs b/kernel/src/syscall/proc.rs
index 533fa43..a6d6d71 100644
--- a/kernel/src/syscall/proc.rs
+++ b/kernel/src/syscall/proc.rs
@@ -1,7 +1,6 @@
 //! Syscalls for process
 
 use super::*;
-use crate::fs::INodeExt;
 
 impl Syscall<'_> {
     /// Fork the current process. Return the child's PID.
@@ -153,9 +152,9 @@ impl Syscall<'_> {
             path, argv, envp
         );
         let mut proc = self.process();
-        let path = unsafe { check_and_clone_cstr(path)? };
-        let args = unsafe { check_and_clone_cstr_array(argv)? };
-        let envs = unsafe { check_and_clone_cstr_array(envp)? };
+        let path = check_and_clone_cstr(path)?;
+        let args = check_and_clone_cstr_array(argv)?;
+        let envs = check_and_clone_cstr_array(envp)?;
 
         if args.is_empty() {
             error!("exec: args is null");